routes: Add better support for taxonomy slugification. * The `site/slugify_mode` can change slugification mode for all sources in one go. * Add support for replacing spaces with dashes. * Add tests.

sudo: false
language: python
python:
  - "3.4"
install:
  - "pip install -r requirements.txt"
  - "pip install -r dev-requirements.txt"
script: py.test